Exchange MVP Jim McBee gives some tips on tuning the Exchange 2003 IMF.
Doug points out some tools for mounting .ISO images (and includes ones that work under Vista).
Finally, the Exchange team blog is giving the standard Exchange 2007 transport rules demo by creating an ethical wall. Now, this is great functionality, but the demo itself is somewhat boring. The last time I did this demo, I spiced it up by eschewing brokers and analysts in favor of putting an ethical firewall in between the military and civilian leadership in Battlestar Galactica. "So sorry, Captain Adama, but you're no longer allowed to foment revolution with President Roslyn." Now that's a demo.